refactor: improve heading revelation logic

Rewrite `addRevealedClasses` to use a two-pass approach that correctly
cascades revealed status from child headings to parent headings. This
ensures that if a sub-heading is revealed, its parent headings are
also treated as revealed, maintaining proper visibility hierarchy.

src/components/Sidebar.tsx

@@ -61,9 +61,6 @@ const SidebarContent: Component<SidebarContentProps> = (props) => {
     if (node.children?.some((child) => !isHeadingHidden(child))) return false;
     return true;
   };
-  createEffect(() => {
-    console.log(currentFileHeadings(), revealedHeadings());
-  });
 
   return (
     <div class="flex flex-col h-full">